Methods of removing metal-containing materials

ABSTRACT

Various methods for selectively etching metal-containing materials (such as, for example, metal nitrides, which can include, for example, titanium nitride) relative to one or more of silicon, silicon dioxide, silicon nitride, and doped silicon oxides in high aspect ratio structures with high etch rates. The etching can utilize hydrogen peroxide in combination with ozone, ammonium hydroxide, tetra-methyl ammonium hydroxide, hydrochloric acid and/or a persulfate. The invention can also utilize ozone in combination with hydrogen peroxide, and/or in combination with one or more of ammonium hydroxide, tetra-methyl ammonium hydroxide and a persulfate. The invention can also utilize ozone, hydrogen peroxide and HCl, with or without persulfate. The invention can also utilize hydrogen peroxide and a phosphate, either alone, or in combination with a persulfate.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/841,706, which was filed May 6, 2004, whichissued as U.S. Pat. No. 7,244,682 on Jul. 17, 2007; and which is herebyincorporated by reference.

TECHNICAL FIELD

The invention pertains to methods of removing metal-containingmaterials, and in particular aspects pertains to methods suitable forincorporation into semiconductor fabrication processes during formationof capacitor constructions.

BACKGROUND OF THE INVENTION

Numerous applications exist in which it is desired to selectively etchmetal-containing materials relative to other materials. One suchapplication is fabrication of capacitor structures during semiconductorprocessing. An exemplary process for forming capacitor structures isdescribed with reference to FIGS. 1-4.

Referring initially to FIG. 1, a semiconductor wafer fragment 10 isillustrated at a preliminary processing stage. Fragment 10 comprises asubstrate 12 supporting a pair of conductive nodes 14 and 16.

Substrate 12 can comprise, for example, monocrystalline silicon lightlydoped with background p-type dopant. To aid in interpretation of theclaims that follow, the terms “semiconductive substrate” and“semiconductor substrate” are defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

Electrical nodes 14 and 16 can comprise, for example, conductively-dopeddiffusion regions extending into a monocrystalline silicon substrate.Alternatively, or additionally, the conductive nodes can compriseelectrically conductive pedestals extending upwardly fromconductively-doped source/drain regions, and surrounded by electricallyinsulative material. Substrate 12 and nodes 14 and 16 are showndiagrammatically in FIG. 1, and it is to be understood that thesubstrate can comprise multiple layers of material, and further that theconductive nodes 14 and 16 can comprise multiple layers of conductivematerial.

An electrically insulative material 18 is formed over substrate 12.Insulative material 18 can comprise any suitable electrically insulativematerial, or combination of electrically insulative materials. Forinstance, material 18 can comprise silicon dioxide, silicon nitride,doped silicon oxide (such as, for example, borophosphosilicate glass(BPSG) or phosphosilicate glass (PSG)), etc.

A pair of openings 20 and 22 extend into insulative material 18. Theopenings are partially filled with a first conductive material 24 whichcan comprise, consist essentially of, or consist of a metal nitride,such as, for example, titanium nitride. First conductive material 24appears to form a pair of sidewall spacers in the shown cross-sectionalview. It is to be understood, however, that the openings 20 and 22 wouldeach have a continuous periphery when viewed from above (typically acircular or elliptical periphery) and accordingly the apparent pair ofspacers 24 shown within each of the openings in the cross-sectional viewof FIG. 1 would actually be a single spacer extending entirely aroundthe periphery of an opening. Material 24 can be formed in the shownconfiguration by depositing the material within the openings and acrossan upper surface of substrate 12. The deposited material will extendacross bottom surfaces of the openings. The material can then be removedfrom over the upper surface of material 18 and from over the bottomsurface of the openings with an appropriate etch, to leave the materialalong the sidewalls of the openings as shown.

A second conductive material 26 is formed within the openings 20 and 22and physically against the first material 24. Second material 26 cancomprise, for example, conductively-doped silicon, such as, for example,conductively-doped polycrystalline silicon. If material 26 comprisessilicon, it can be undoped at the processing stage of FIG. 1.Accordingly the silicon can be electrically insulative, rather than inthe shown electrically conductive form. Thus, material 26 can be asilicon material which is doped at a processing stage subsequent to thatof FIG. 1, or it can be a silicon material which is doped prior to theprocessing stage of FIG. 1.

The wafer fragment 10 is shown divided into a first segment 30 and asecond segment 32. The segments 30 and 32 can correspond to, forexample, a memory array region and a region peripheral to the memoryarray region, respectively.

Referring to FIG. 2, first conductive material 24 (FIG. 1) isselectively etched relative to materials 26 and 18, which forms openings36 between materials 26 and 18. If material 18 comprises silicondioxide, silicon nitride, and/or doped oxide; material 26 compriseseither doped or undoped silicon; and material 24 comprises a metalnitride (such as, for example, titanium nitride), the etching willtypically be conducted with one of three etchant solutions. Such etchantsolutions are: (1) sulfuric acid (H₂SO₄)/hydrogen peroxide (H₂O₂); (2)H₂O₂/hydrochloric acid (HCl); and (3) H₂O₂/ammonium hydroxide (NH₄OH).The H₂SO₄/H₂O₂ solution will typically comprise a ratio of sulfuric acid(provided as a commercially available solution of sulfuric acid andwater) to hydrogen peroxide (provided as commercially available hydrogenperoxide solution that is about 30 weight percent hydrogen peroxide inwater) of from about 10:1 to about 2:1.

The H₂O₂/HCl solution will typically be formed by mixing about 5 partswater with about 1 part hydrogen peroxide (provided as commerciallyavailable hydrogen peroxide solution that is about 30 weight percenthydrogen peroxide in water) and about 1 part hydrochloric acid (providedas commercially available hydrochloric acid, which is about 29 weightpercent HCl in water). The final solution will comprise about 92 weightpercent water, about 4.3 weight percent hydrogen peroxide, and about 4.1weight percent hydrochloric acid.

The H₂O₂/NH₄OH solution will typically be formed by mixing about 10parts water with about 1 part hydrogen peroxide (the 30 weight percenthydrogen peroxide) and about 1 part ammonium hydroxide(provided ascommercially available ammonium hydroxide, which is about 29 weightpercent NH₄OH in water). Accordingly, the final solution will typicallycomprise about 95 weight percent water, about 2.5 weight percenthydrogen peroxide, and about 2.4 weight percent ammonium hydroxide.

The solutions discussed above are typically utilized at a temperature offrom about 50° C. to about 75° C.

Although FIG. 2 shows the etch of the metal nitride material (24 ofFIG. 1) as being highly selective relative to materials 18 and 26, suchis typically not the case. Instead, some of materials 26 and 18 areremoved during the etching of material 24. Removal of materials 26 and18 decreases the height of materials 18 and 26, and can also increasethe width at the upper locations of openings 36 relative to the lowerlocations of openings 36.

The non-selectivity of the etch becomes increasingly problematic as anaspect ratio of openings 36 increases. In modern processing, it can bedesired that material 18 have a thickness of 20,000 Å or more, and thatopenings 36 are formed to have a width of from about 30 Å to about 150Å. Accordingly, openings 36 are long capillaries. Etching within thecapillaries is slower than etching of surfaces external to thecapillaries (with the etching frequently being nearly eight-times slowerin the capillaries than along surfaces external to the capillaries).Accordingly, unless the etch for the material 24 (FIG. 1) is highlyselective, there will be significant loss of materials 18 and 26 duringthe etch. Such is a problem with conventional etching processes.

The upwardly-open structures defined by material 26 can be storage nodesfor capacitor constructions. The two illustrated storage nodes arelabeled as 27 and 29, respectively.

Referring to FIG. 3, the material 18 remaining after formation ofopenings 36 (FIG. 2) is subjected to an isotropic etch to remove thematerial 18 from between storage nodes 27 and 29. Since the etchantsolution can penetrate into openings 36 (FIG. 2) the material 18 betweenstructures 27 and 29 is subjected to etching from all sides during theisotropic etch, whereas the material 18 over region 32 is subjected toetching from the upper surface only. The material 18 over region 32 isthus removed more slowly than the material 18 between structures 27 and29. Accordingly, some of material 18 remains over region 32 afterremoval of all of the material from between structures 27 and 29. It isdesired to leave material 18 over region 32 after the isotropic etch ofmaterial 18, so that the material 18 can protect circuit devicestructures (not shown) associated with region 32 during subsequentprocessing.

The structure shown in FIG. 3 is an idealized prior art structure, and a“hoped for” structure during the processing of FIGS. 1-3. The structurecan result if openings 36 (FIG. 2) have a low enough aspect ratio, sothat the non-selectivity of the prior art etch does not significantlyimpact the height of material 18 during removal of material 24 (FIG. 1)in formation of openings 36 (FIG. 2). However, if the openings have ahigh enough aspect ratio, the non-selectivity of the etch willsignificantly reduce the height of material 18 during formation ofopenings 36. If the height of material 18 is reduced too much, thedesired structure of FIG. 3 will not result. Instead, material 18 willbe removed from over both of regions 30 and 32 during the isotropic etchof material 18.

Referring to FIG. 4, a capacitor dielectric material 40 and a secondcapacitor electrode 42 are formed over capacitor storage nodes 27 and29. Capacitor dielectric material 40 can comprise any suitable material,or combination of materials, including, for example, silicon dioxide,silicon nitride, and various high-K materials. Electrode 42 can beformed of any suitable conductive material, including, for example,conductively-doped silicon, and/or various metals, and/or various metalcompounds. If material 26 comprises undoped silicon at the processingstage of FIGS. 1-3, the silicon will typically be conductively-dopedprior to formation of dielectric material 40 and electrode 42. Suchdoping can be accomplished utilizing various suitable methods including,for example, an implant directly into material 26.

Conductive material 42 is spaced from conductive material 26 bydielectric material 40, and accordingly conductive material 42,dielectric material 40 and storage nodes 27 and 29 form a pair ofcapacitor constructions 44 and 46. The capacitor constructions can beconnected with transistor devices (not shown) and utilized as dynamicrandom access memory (DRAM) cells, as will be understood by persons ofordinary skill in the art. Materials 40 and 42 are not shown extendingover peripheral region 32 in the shown aspect of the prior art. However,it is to be understood that the materials 40 and 42 could also be formedover peripheral region 32 in accordance with some prior artmethodologies.

A difficulty in conducting the above-described prior art processingoccurs during removal of material 24 (FIG. 1), and results from a lackof a suitably selective etch chemistry having a sufficiently high etchrate to perform in high aspect ratio features. It is therefore desiredto develop new etch chemistries having higher selectivity formetal-containing materials (such as, for example, metal nitrides)relative to silicon nitride, silicon dioxide and/or doped silicon oxide.

SUMMARY OF THE INVENTION

The invention encompasses numerous chemistries which can be utilized forselectively etching metal-containing materials. In particular aspects,the chemistries can be utilized for selectively etching metal nitriderelative to one or more of silicon (such as, for example, either dopedor undoped polycrystalline and/or amorphous silicon), silicon dioxide,silicon nitride, and doped silicon oxide.

In one aspect, an exemplary chemistry of the present invention utilizeshydrogen peroxide in combination with ammonium hydroxide or tetra-methylammonium hydroxide. The etchant solution can be formed by mixing about400 parts of 30 weight percent hydrogen peroxide with about 5 parts of25 weight percent tetra-methyl ammonium hydroxide or 29 weight percentammonium hydroxide.

In one aspect, an exemplary chemistry utilizes hydrogen peroxide andhydrochloric acid, with such solution being formed by mixing about 30weight percent hydrogen peroxide with about 35 weight percenthydrochloric acid in a volume ratio of 400:20.

In other exemplary aspects, chemistries of the present invention utilizea persulfate (such as ammonium persulfate) with hydrogen peroxide, ozonewith hydrogen peroxide, a persulfate with hydrogen peroxide and ammoniumhydroxide, or a persulfate with hydrogen peroxide and tetra-methylammonium hydroxide.

In other exemplary aspects, chemistries of the present invention utilizeozone with ammonium hydroxide and/or tetra-methyl ammonium hydroxide, orutilize ozone in combination with hydrogen peroxide and hydrochloricacid.

In other exemplary aspects, chemistries of the present invention utilizehydrogen peroxide with a phosphate (such as, for example, ammoniumphosphate dibasic, (NH₄)₂HPO₄, either alone, or in combination with apersulfate (such as, for example, ammonium persulfate).

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment shown at a preliminary processing stage of a prior art methodfor forming capacitor constructions.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a prior artprocessing stage subsequent to that of FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a prior artprocessing stage subsequent to that of FIG. 2.

FIG. 4 is a view of the FIG. 1 wafer fragment shown at a prior artprocessing stage subsequent to that of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention encompasses several new etch chemistries which can beutilized for selectively removing metal-containing materials. Themetal-containing materials can, in particular aspects, comprise, consistessentially of, or consist of metal nitrides, such as, for example,titanium nitride. The etching of the present invention can selectivelyremove the metal-containing materials relative to materials comprising,consisting essentially of, or consisting of silicon (either doped orundoped), doped silicon oxide (such as, for example, BPSG), silicondioxide, and/or silicon nitride.

In particular aspects, the metal-containing material consistsessentially of, or consists of titanium nitride, and such material isselectively removed relative to a material consisting essentially of orconsisting of silicon (either doped or undoped, and which can be in theform of, for example, polycrystalline and/or amorphous), and a materialconsisting essentially of, or consisting of doped silicon oxide (such asBPSG).

The etching solutions of the present invention, when utilized underconditions discussed below, can have a selectivity for the metal nitriderelative to the silicon and the doped silicon oxide of at least 600:1(i.e., can remove the metal nitride at a rate at least 600 times greaterthan the rate of removal of the other materials), and in particularaspects can have a selectivity of at least 10,000:1, or at least16,000:1.

Etching solutions of the present invention are preferably utilized attemperatures higher than the conventional temperatures discussed in the“Background” section of this disclosure, and specifically wouldgenerally be maintained at temperatures of from about 65° C. to about95° C. during an etch, and preferably are utilized at temperatures offrom about 85° C. to about 95° C., with temperatures of from about 85°C. to about 90° C. being typical.

In some aspects, the invention includes a recognition that there can beadvantages to utilizing minimal amounts of acids and bases with theperoxide or other oxidants to accomplish selective removal ofmetal-containing materials relative to materials consisting essentially,or consisting of silicon (doped or undoped), silicon nitride, silicondioxide and/or doped silicon oxide. The amount of oxidant in particularetching solutions of the present invention can be increased relative toprior art etching solutions by not adding water to the etching solutionsof the present invention. Many of the components utilized in etchingsolutions of the present invention are generally in the form of aqueoussolutions. For instance, hydrogen peroxide is generally available as asolution of about 30% hydrogen peroxide (by weight) in water and HCl isavailable as a solution of about 35% HCl (by weight) in water. Theavailable solutions of the HCl and hydrogen peroxide can be consideredstarting components for forming a solution of the present invention. Insome aspects, the components of a solution are mixed to form thesolution of the present invention without addition of any water beyondthat available with the components. Thus, if a solution was formed fromthe HCl and hydrogen peroxide components discussed above, the solutionwould not contain water beyond that present with the HCl and hydrogenperoxide in the starting components.

In one aspect of the invention, an etching solution comprises hydrogenperoxide and ozone. Such etching solution can consist essentially of, orconsist of hydrogen peroxide, ozone and water, or alternatively canconsist essentially of, or consist of hydrogen peroxide, ozone, waterand a suitable material (such as HCl) to render the solution acidic, oras yet another alternative can consist essentially of, or consist ofozone, hydrogen peroxide and water and a suitable material (such as TMAHor NH₄OH) to render the solution basic.

An exemplary solution comprises, consists essentially of, or consists ofhydrogen peroxide, ozone, hydrochloric acid and water. It is to beunderstood that the solution will typically comprise various ionizedforms of the materials contained therein, such as, for example, hydrogenions (protons) and chlorine ions from hydrochloric acid. Accordingly, asolution referred to herein as consisting of hydrochloric acid, ozone,hydrogen peroxide and water is to be understood to include variousionized forms of the compounds specified as being contained therein.Also, it is to be understood that a solution will consist of particularchemistries described herein when the solution is initially made, andwhen exposure of the solution to a metal-containing material isinitiated. The composition of the solution can then change as theetching of the metal-comprising material is conducted, and specificallyas various components of the metal-comprising material are solvated.

In some aspects, the etchant solution can comprise ozone, hydrogenperoxide, and ammonium. The ammonium can be provided in an initialsolution with the hydrogen peroxide, and subsequently such initialsolution can be mixed with ozone in a suitable spray apparatus. The formof ammonium provided in the initial solution can be, for example,ammonium hydroxide, ammonium persulfate, and/or diammonium phosphate(also called ammonium phosphate dibasic). In similar aspects, theetchant solution can comprise ozone, hydrogen peroxide, and tetra-methylammonium hydroxide.

In another aspect of the invention, a metal-containing material, suchas, for example, a material comprising, consisting essentially of, orconsisting of metal nitride, such as titanium nitride, is removed with asolution comprising hydrogen peroxide and a strong oxidizer, such as,for example, persulfate. The persulfate can be initially provided in thesolution as ammonium persulfate, and accordingly the solution cancomprise, consist essentially of, or consist of hydrogen peroxide,ammonium persulfate, and water. In further aspects of the invention, aphosphate can be mixed with the solution comprising hydrogen peroxideand persulfate. The phosphate can be, for example, diammonium phosphate.A suitable solution can be formed by mixing hydrogen peroxide, ammoniumpersulfate, and diammonium phosphate.

The diammonium phosphate can function as a buffering agent.Specifically, a solution of H₂O₂ and ammonium persulfate is mildlyacidic (pH<5). A basic solution can be preferred in order to reduceparticulate contamination. Diammonium phosphate can drive the pH towardneutral and act as buffering agent to maintain the pH in a desiredslightly basic range. The inclusion of diammonium phosphate can boostthe overall etch rate of the H₂O₂ and ammonium persulfate solution. Anadvantage of utilizing diammonium phosphate relative to other basicagents is that it has less etching of polysilicon (such as material 26of FIGS. 1-4) than some other basic agents (such as ammonium hydroxide,for example).

In yet other aspects of the invention, a solution can be formedcomprising, consisting essentially of, or consisting of hydrogenperoxide and ammonium persulfate, together with one or both of ammoniumhydroxide and tetra-methyl ammonium hydroxide. An advantage oftetra-methyl ammonium hydroxide can be better selectivity towardpolysilicon than is achieved with other agents (such as ammoniumhydroxide).

In another aspect, an etching solution utilized to remove a materialcomprising, consisting essentially of, or consisting of metal nitride,such as, for example, titanium nitride, comprises hydrogen peroxide anda phosphate. The phosphate can be initially provided in a solution withthe hydrogen peroxide as a diammonium phosphate, and accordingly thesolution can comprise, consist essentially of, or consist of hydrogenperoxide, ammonium phosphate and water.

In another aspect, a solution utilized for removing a materialcomprising, consisting essentially of, or consisting of metal nitride(such as, for example, titanium nitride) comprises at least about 10weight percent hydrogen peroxide and from greater than 0 weight percentto less than 2 weight percent of a nitrogen-containing compound. Thenitrogen-containing compound can be, for example, ammonia or ammonium,and in particular aspects can be initially provided in a solution asammonium hydroxide and/or diammonium phosphate. The nitrogen-containingcompound can alternatively be tetra-methyl ammonium, and can beinitially provided in a solution as tetra-methyl ammonium hydroxide. Insome aspects, the solution can comprise, consist essentially of, orconsist of hydrogen peroxide, water and NH₄OH, with the NH₄OH beingpresent to a concentration of from about 0.15 weight percent to about 2weight percent and the hydrogen peroxide being present to aconcentration of from about 25 weight percent to about 30 weightpercent. In some aspects, the solution can comprise, consist essentiallyof, or consist of hydrogen peroxide and tetra-methyl ammonium hydroxide,with the tetra-methyl ammonium hydroxide being present to aconcentration of from about 0.25 weight percent to about 1 weightpercent and the hydrogen peroxide being present to a concentration offrom about 25 weight percent to about 30 weight percent.

In another aspect, the invention encompasses a method of removing amaterial comprising, consisting essentially of, or consisting of metalnitride (such as, for example, titanium nitride) in which the materialis exposed to a solution comprising at least 10 weight percent hydrogenperoxide and from greater than 0 weight percent to less than 2 weightpercent of a strong acid. The strong acid can be, for example,hydrochloric acid. Accordingly, the solution can consist of hydrogenperoxide, water and hydrochloric acid when the solution is initiallymade, and when exposing of the metal nitride-containing material to thesolution is initiated. In particular aspects, the solution will beformed to comprise, consist essentially of, or consist of hydrogenperoxide, hydrochloric acid and water. The weight percentage of thehydrogen peroxide in the solution can be from about 25 to about 30, andthe weight percentage of the hydrochloric acid in the solution can befrom about 0.5 to about 2.5, and in some aspects can be from about 1 toabout 2.

Various potential roles and effects of particular materials that arepresent in exemplary etch solutions are as follows. The oxidizingcomponents can etch TiN at a high etch rate; the strong acid (e.g. HCl)can boost an etch rate; the diammonium phosphate can be a buffer andassist in maintaining etch selectivity relative to polysilicon andBPSG); the ammonium hydroxide and TMAH can provide a basic solutionwhich can reduce contamination but which can also reduce selectivitytoward polysilicon and can cause pinholes; the EDTA can assist in masstransfer of reaction by-products form capillaries. The roles areprovided to assist the reader in understanding aspects of the invention,and are not to be construed as limiting the invention.

Methodologies of the present invention can be utilized for formingcapacitor constructions of the type described with reference to FIGS.1-4. Accordingly, in various methodologies of the present invention, anelectrically insulative material (such as the material 18 of FIG. 1) canbe formed over a semiconductor substrate (such as substrate 12 of FIG.1). An opening is formed into the insulative material, such as theopening 20 or 22 of FIG. 1, and such opening has at least one sidewall.A metal-containing material (such as the material 24 of FIG. 1) isformed along the at least one sidewall of the opening. Asilicon-containing material (such as the material 26 of FIG. 1) isformed along the metal-containing material. An etch conducted inaccordance with the present invention can then be utilized forselectively removing the metal-containing material relative to theinsulative material and the silicon-containing material, with such etchhaving a selectivity for the metal-containing material of at least600:1, and in some aspects of at least about 1,000:1, of at least about10,000:1 or even 16,000:1.

As discussed above with reference to FIGS. 1-4, a problem with prior artetch chemistries is that such are not sufficiently selective formetal-containing materials, such as, for example, metal nitrides, liketitanium nitride. The prior art etch chemistries do not satisfactorilyremove the metal-containing materials from a thin capillary of the typedescribed with reference to FIGS. 1-3 while not removingsilicon-containing materials or various insulative materials.Frequently, the etching into the high aspect capillaries of the typedescribed with reference to FIGS. 1-4 will be at least about 8 timesslower than normal surface etching. Accordingly, a 5% decrease in therelative etch rate of a metal-containing material to other materials fora high aspect ratio etch of the metal-containing material can equate toa huge increase in the normal surface etching, and accordingly canequate to a significant problem for a process of the type described withreference to FIGS. 1-4.

The metal-containing material 24 described above with reference to FIGS.1-4 will typically comprise, consist essentially of, or consist of oneor more metal nitrides, with a typical metal nitride being titaniumnitride. Also, as discussed previously, the silicon-containing material26 can comprise, consist essentially of, or consist of either doped orundoped silicon material, with typical silicon materials beingpolycrystalline silicon and/or amorphous silicon. Additionally, asdiscussed above, insulative material 18 can comprise, consistessentially of, or consist of one or more of silicon nitride, silicondioxide and doped silicon oxide (such as BPSG and/or PSG). Etchingchemistries of the present invention can be selective formetal-containing materials (and specifically for metal nitrides, suchas, for example, titanium nitride) relative to at least one of, andtypically all of, doped or undoped polycrystalline or amorphous silicon,silicon nitride, silicon dioxide and doped silicon oxide. Accordingly,methodology of the present invention can be particularly useful forapplication to the capacitor-forming process of FIGS. 1-4.

As discussed above with reference to FIGS. 1-4, it can be desired thatthe openings formed by removal of the metal-containing material (theopenings 36 in FIG. 2) have a very high aspect ratio, with preferredopenings having a depth of at least about 20,000 Å, and a width (the gapbetween insulative material 18 and silicon-containing material 26) offrom about 75 Å to about 150 Å. Preferably, such width will bemaintained along the entire depth of the opening. Accordingly, it ispreferable that an etch of the present invention remove substantiallyall, or preferably entirely all, of the metal-containing material (24 ofFIG. 1) in forming the openings (36 of FIG. 2).

After etching of the present invention has been utilized to formopenings analogous to the openings 36 of FIG. 2, the processingdescribed previously with reference to FIGS. 3 and 4 can be conducted toform capacitor constructions. Accordingly, insulative material 18 can beisotropically etched to leave remaining storage node structures of thesilicon-containing material (such as the structures 27 and 29 of FIGS. 3and 4), a capacitor dielectric (such as the material 40 of FIG. 4) canbe formed over the remaining structures, and a conductive material (suchas the conductive material 42 of FIG. 4) can be formed over thecapacitor dielectric material.

Although not mentioned above, it is to be understood that various of thesolutions of the invention described above can comprise ametal-scavenging composition (such as a suitable chelator, with anexemplary chelator being ethylenediaminetetraacetic acid (EDTA)) inaddition to the other materials discussed. If EDTA is utilized, it canbe provided to a concentration of about a few milligrams per liter ofsolution.

Various examples are described below to assist the reader inunderstanding the invention. It is to be understood that the inventionis not limited to such examples, except to the extent, if any, that oneor more of the examples are specifically recited in the claims thatfollow.

Example 1

An etching solution is formed by mixing 400 parts of hydrogen peroxidewith 5 parts of ammonium hydroxide. The hydrogen peroxide is 30 weightpercent in water and the ammonium hydroxide is 29 weight percent inwater. Accordingly, the final solution comprises approximately 30 weightpercent hydrogen peroxide, 0.36 weight percent ammonium hydroxide, and70 weight percent water.

Example 2

An etching solution is formed by mixing 400 parts of hydrogen peroxidewith 5 parts of tetra-methyl ammonium hydroxide. The hydrogen peroxideis 30 weight percent in water and the tetra-methyl ammonium hydroxide is25 weight percent in water. Accordingly, the etching solution comprises30 weight percent hydrogen peroxide, 0.31 weight percent tetra-methylammonium hydroxide, and 70 weight percent water.

Example 3

An etching solution is formed by mixing 400 parts of hydrogen peroxidewith 20 parts of hydrochloric acid. The hydrogen peroxide is 30 weightpercent in water and the hydrochloric acid is 35 weight percent inwater. Accordingly, the etching solution comprises about 29% hydrogenperoxide, 1.7% hydrochloric acid, and 69% water.

Example 4

An etching solution is formed by providing greater than 0% ammoniumpersulfate (as measured in grams of ammonium persulfate per milliliterof solution) in hydrogen peroxide (with the hydrogen peroxide being 30weight percent in water). The ammonium persulfate is typically providedto a concentration of less than 40% (as measured in grams of ammoniumpersulfate per milliliter of solution), with about 21% ammoniumpersulfate being an exemplary concentration.

Example 5

An etching solution is formed by mixing ozone with hydrogen peroxide.The hydrogen peroxide is 30 weight percent in water. The mixing isconducted in a spray apparatus (such as for example, an apparatusdistributed as SCEPTER™ by Semitool™) by flowing the ozone at a rate offrom about 180 milligrams per liter (mg/L) to about 270 mg/L mixed with3 L to 8 L of deionized water, and by flowing the hydrogen peroxide at arate of from about 3 to about 7 liters/minute.

Example 6

Ammonium persulfate in the concentration range discussed above withreference to Example 4 is provided in the solution of Example 1.

Example 7

Ammonium persulfate in the concentration of Example 4 is provided intothe tetra-methyl ammonium hydroxide etching solution of Example 2.

Example 8

Ozone is provided with the etching solution of Example 1. The etchingsolution of Example 1 is flowed into a spray apparatus at a flow rate offrom about 3 to about 7 liters/minute, and ozone is flowed into theapparatus at the flow rate of from about 180 milligrams per liter (mg/L)to about 270 mg/L mixed with 3 L to 8 L of deionized water.

Example 9

Ozone is mixed with the etching solution of Example 2. The ozone ismixed into the solution utilizing a spray apparatus and a flow rate ofthe ozone of from about 180 milligrams per liter (mg/L) to about 270mg/L mixed with 3 L to 8 L of deionized water, and a flow rate of theetch solution of Example 2 of from about 3 to about 7 liters/minute.

Example 10

Ozone is mixed with the hydrochloric acid/hydrogen peroxide etchingsolution of Example 3. The ozone is flowed into a spray apparatus at aflow rate of from about 180 milligrams per liter (mg/L) to about 270mg/L mixed with 3 L to 8 L of deionized water, and the HCl/H₂O₂ solutionis flowed into the spray apparatus at a flow rate of from about 3 toabout 7 liters/minute.

Example 11

An etching solution comprising hydrogen peroxide, ammonium persulfateand ammonium phosphate is formed. The solution can be formed by mixing400 milliliters of hydrogen peroxide (30 weight percent in water) withabout 20 grams of (NH₄)₂HPO₄, and with about 60 grams of ammoniumpersulfate.

Example 12

An etching solution comprising ammonium peroxide and ammonium phosphateis formed. Approximately 20 grams of (NH₄)₂HPO₄ are provided in about400 mils of hydrogen peroxide (30 weight percent in water).

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of removing metal-containing material comprising: exposingthe metal-containing material to a solution comprising H₂O₂ and aphosphate; wherein the metal-containing material is received betweenpolycrystalline silicon and borophosphosilicate glass; wherein thesolution has a selectivity for removing the metal-containing materialrelative to the polycrystalline silicon and the borophosphosilicateglass of at least 600:1; and wherein the removing of themetal-containing material forms a space between the polycrystallinesilicon and the borophosphosilicate glass.
 2. The method of claim 1wherein the selectivity for removing the metal-containing materialrelative to the polycrystalline silicon and the borophosphosilicateglass is at least 10,000:1.
 3. The method of claim 1 wherein themetal-containing material comprises a metal nitride.
 4. The method ofclaim 3 wherein the metal-containing material consists essentially ofthe metal nitride.
 5. The method of claim 3 wherein the metal-containingmaterial consists of the metal nitride.
 6. The method of claim 1 whereinthe metal-containing material comprises titanium nitride.
 7. The methodof claim 1 wherein the metal-containing material consists essentially oftitanium nitride.
 8. The method of claim 1 wherein a temperature of thesolution is maintained at from about 65° C. to about 95° C. during theexposing.
 9. The method of claim 8 wherein the temperature of thesolution is maintained at from about 85° C. to about 95° C. during theexposing.